1. Field of the Invention
The present invention relates to a method of manufacturing a turbine nozzle.
2. Description of the Related Art
Conventionally. in a steam turbine used for a power generation plant, a turbine stage is constructed in a manner of combining a turbine nozzle (turbine stationary blade) and a turbine rotor blade.
The turbine nozzle of the turbine stage converts a steam energy into a velocity energy, and then, gives the velocity energy to a turbine rotor blade so as to rotate the turbine rotor blade, and thus, generates a rotating torque in a turbine shaft.
The latest turbine nozzle has a structure as shown in FIG. 13. More specifically, the turbine nozzle has a blade body nozzle blade body) 1 which is provided with a bottom portion (inner side portion) 2 to be supported by a support plate of inner ring side, a tip portion (head portion, outer side portion) 3 to be supported by a support plate of outer ring side and an intermediate portion 4 connecting the bottom portion 2 and the tip portion 3.
The intermediate portion 4 is provided with straight tilted portions TL which are formed to extend toward an inner concave side (abdominal side) 5 from respective bottom and head portions 2 and 3 of the blade body 1 with respect to a radius line RL passing through the center of the turbine shaft.
The intermediate portion 4 is provided with a curved portion CL which projects in a downstream side and connects the straight tilted portions TL. In this manner, a so-called compound lean type three-dimensional blade profile is realized. The turbine nozzle having the three-dimensional blade profile can reduce a secondary flow loss as compared with a turbine nozzle having a two-dimensional blade profile: therefore, it is possible to greatly improve a blade efficiency of the turbine nozzle.
In the case of inserting the above-described nozzle blade body 1, which is excellent in a flowing characteristic, between a support plate 6 of inner ring side of the nozzle and a support plate 7 of outer ring side thereof, there are some Problems.
First, in each of the support plates 6 and 7, a profile of each hole of each of the support plates 6 and 7 is two-dimensional; on the contrary, a blade profile of the nozzle blade body 4 is three-dimensional. For this reason, it is difficult to carry out the work for adjusting and positioning the nozzle blade body 4 to each hole of each support plate 6, 7 so as to insert that thereinto, so that, in the case where the nozzle blade body 4 is not positioned to each of the support plates 6 and 7 so as not to be inserted therein, it must be necessary to carry out a machining finish of each of inner surfaces of each of the holes of each of the support plates 6 and 7, whereby it takes much time to carry out the machining finish work.
That is, the positioning and adjusting works, the machining finish works and so on are repeatedly carried out when inserting the plurality of nozzle blade main bodies 1 into corresponding respective holes of the respective support plates 6 and 7, and therefore, there is a problem that a worker for the positioning and adjusting works and the machining finish works is forced to have a much labor.
In particular, labor and time have been spent for insertion, position and adjustment works in the vicinity of a leading edge 11 and a trailing edge 12 of the nozzle blade body 1 with respect to a hole of each of the support plates 6 and 7. Next, in order to shorten a time for inserting and positioning the nozzle blade body 1 between the support plates 6 and 7, there are many cases where an edge of each and face on a blade root portion 2 side and a blade chip portion 3 side of the nozzle blade body 1 is subjected to chamfering. In this case, each hole shape of the support plates 6 and 7 is different from a blade profile of the nozzle blade body 1 for this reason, a TIG welding time for filling up the chamfered portion of the nozzle blade body 1 becomes considerably long so that there is a problem that a bad influence is given to a quality guarantee of base material of the turbine nozzle, and a cost of manufacturing the turbine nozzle becomes high.